This invention relates to a waveform to pulse conversion technique and more particularly to techniques for converting arbitrary analog waveforms to sequences of pulses.
Pulse generators are well known, for example, for DC controllers and other applications. However, the typical pulse generator is an adaptation of a conventional oscillator or monostable multivibrator, which can produce undesired or spurious transients when the pulse triggering is terminated. Such transients could be confused with trailing pulses, so that the counting of pulses is an inaccurate representation of the intended pulse count.
A typical pulse generator is responsive to a trigger related to a threshold level; that is, pulses are generated when a level input is applied that exceeds a predetermined threshold that has established a trigger point. The duration of the input above the threshold typically corresponds to the duration of the pulse train or oscillation period.
A classic van der Pol (vdP) oscillator is a simple nonlinear oscillator circuit and is a useful starting point for use as a pulse generator. However, the classic vdP oscillator is not readily tunable.
Circuitry is needed which is simple and yet which addresses needs in specialized applications.
According to the invention, a method and apparatus are provided for generating output pulses or oscillations in response to input analog waveforms which involves exciting, with a known but arbitrary analog waveform, a circuit with a variable operating point and having a transfer function characterized by an unstable operating region bounded by a first stable operating region and a second stable operating region, the analog waveform having a first information region and a second information region, then, responsive to the sensing of the first information region, forcing the variable operating point to vary in order to initiate operation of the circuit in the unstable operating region to produce a sequence of oscillations at a frequency greater than rate of change of the operating point; and then responsive to the sensing of the second information region, forcing the variable operating point to vary into either one of the stable operating regions in order to terminate the oscillations, such that the initiating and terminating of oscillations alternate. The result is a mapping of each cycle of the input waveforms to a sequence of pulses separated by silences. The circuit or device according to the invention is a form of oscillator having an N-shaped or S-shaped V-I characteristic that operates nonlinearly; that is, to oscillate during excursion of current and voltage through a unstable operating region. A variety of input waveforms may map to a particular string of pulses. Decoding is not for the purpose of identifying the type of input waveforms. One application is expressing information represented by the waveforms. For example, a character set could be mapped to one or more cyclical waveforms.